In today's world, water sources for human consumption or other uses can often contain contaminants and various pollution elements such as pathogens which may cause various infections (e.g. bacteria, viruses, etc.) and organic and inorganic substances which may cause unwanted odor and color to the water sources. Naturally it is desired to reduce the amount of contaminants in water, especially if the water is destined to be consumed by people.
In the past, water treatment systems have been mainly managed by municipalities, in order to accommodate the drinkable and recreational water needs of their population, and also treat waste water. Lately, the increasing concerns regarding the environment, the standards associated to its protection and the emergence of larger scale projects in construction have changed the requirements and the mission of water treatment systems. Also, available water sources can be of different nature, including surface waters or ground water.
These days, water treatment systems need to be more adaptable to various types of environments. They must use products and offer water quality following very strict environmental regulations and at the same time, be less expensive to be attractive to smaller municipalities and private interests.
Previous methods and systems for reducing contaminants in water have used, for example chlorine and ozone. Of these substances ozone has recently become more and more popular since ozone is one of the most powerful oxidizers and disinfectants available.
On the one hand, the most commonly used disinfectants are hypochlorous acid (HOCl) and hypochlorite (OCl−) (customarily referred to as free chlorine in the industry). Also used but to a lesser degree are hypobromous acid (HOBr) and hypobromite (OBr−) (likewise, referred to as free bromine). However, most compounds that produce chlorine in water sources influence the pH thereof. It is therefore necessary to add either an acidic or a caustic substance to maintain a certain pH. This means that the water treatment systems need to have two injection systems: one for the selected disinfectant, and another one for the pH control.
On the other hand, ozone exhibits biocidal qualities in concentrations over 0.4 parts per million, when dissolved in water. Ozone is a semi-stable gas formed of three oxygen atoms, instead of the two atoms that form oxygen gas. Ozone is most typically produced by an electrical arc discharged through air causing oxygen atoms to combine with an oxygen free radical that is formed. Ozone rapidly undergoes reaction to revert to more stable oxygen, releasing an oxygen free radical in the process. Two such free radicals can combine to form an oxygen molecule or the free radicals can oxidize an oxidizable substance.
Ozone not only kills bacteria, but also inactivates many viruses, cysts and spores. In addition, ozone oxidizes many organic chemical compounds, including chloramines, soaps, oils and other wastes thereby rendering them harmless to the environment. Accordingly, ozone may be used for a number of purposes, including: purification of water used for drinking, in food cleaning and processing, in ice machines, in swimming pools and spas and waste water treatment.
Although ozone is especially beneficial for breaking down certain contaminants in water, obtaining an effective concentration of ozone in water may be difficult and may represent a more expensive solution in a water treatment system. At a high concentration, ozone is a toxic and corrosive gas which is considered to be a pollutant by The United States Environmental Protection Agency (EPA), such that special provisions must be made for the containment and removal of the excess ozone.
Though the use of ozone in water treatment apparatuses and systems has generally proven to be effective, it remains that ozone can seldom be used alone since some pollutants need to be physically removed from the water. Hence, in prior art water treatment apparatuses and systems, ozone treatments were generally combined with filtration treatments, before and/or after the ozone treatments, in order to remove larger pollutants and/or particles from the water. For example, U.S. Pat. No. 5,427,693 (Mausgrover), U.S. Pat. No. 5,711,887 (Gastman) and U.S. Pat. No. 6,464,877 (Mori) all teach such prior art apparatuses or systems.
Yet, one major drawback of prior art water treatment apparatuses and systems is the need to regularly clean the filters which tend to become clogged with pollutants over time. Generally, cleaning filters implies the physical and/or chemical cleaning of the filters. This, in turn, necessitates that the apparatus or system be shut down while the filters are cleaned or changed.
Notwithstanding the existence of prior art ozone water treatment apparatuses and systems, it remains clear there is a need for an improved water treatment apparatus which mitigates the shortcomings of the prior art apparatuses and systems.